Illuminating surface

ABSTRACT

The present invention provides an illuminating surface, e.g. a floor or wall tile, that includes an array of identical circuits (G, K, H, L) that can each be connected to a power source / 14 ). The surface emits light in the presence of an object touching or in close proximity to the surface. Each circuit includes a sensor ( 12 ), e.g. a pressure switch, for detecting the presence of the object; at least one light source ( 20 ) that is illuminated when the sensor of that circuit detects the presence of the object. The circuits control the illumination of the light sources ( 20 ) such that the light sources remains illuminated for a time after its associated sensor ( 12 ) has ceased to detect the presence of the object. Each of the circuits is connected with at least one adjacent circuit, and, when the sensor of the first-mentioned circuit detects the presence of an object, the light source(s) ( 20 ) of the adjacent circuits are illuminated, thereby causing an area of the surface to emit light that corresponds to and is larger than the shape of the object.

TECHNICAL FIELD

The present invention relates to an illuminating surface that emitslight in the presence of an object touching or in close proximity to thesurface.

It is known to use light emitting tiles to form a floor or ceilingpanels. It is also known that the illumination given by such panels canbe touch-sensitive. This is achieved, according to a known arrangement,by providing a gel layer between a light source and the front surface ofthe panel; when the gel layer is pressed, it becomes thinner in thatregion and accordingly allows more light to pass to the front surface.In time, the gel returns to a uniform thickness, thereby causing thelight to emit uniform illumination once again.

It is also known to mark out a path to be followed using individuallight sources; such an arrangement is known, for example, in aircraft tomark the path to emergency exits.

When used as floor tiles, it would be advantageous to emit light notonly from the area being touched but also from adjacent areas so that,if the rest of the room is dark, light can escape from the adjacentareas to provide illumination for a person crossing the floor, e.g. achild looking for the toilet in the middle of the night. It is alsodesirable, for the same reason, that light is still emitted even after aperson's foot has been lifted from the floor so that the path of theperson remains illuminated. Such an arrangement can also be useful forsecurity purposes to show that a person has crossed a floor and wherethat person has gone.

DISCLOSURE OF INVENTION

According to the present invention, there is provided an illuminatingsurface that, when connected to a power source, emits light in thepresence of an object touching or in close proximity to the surface,which surface comprises: an array of sensors for detecting the presenceof the object (which will in many applications be a person's foot orhand); an array of light sources, each sensor being associated with atleast one light source such that, when one of said sensors detects thepresence of the object, its associated light source is illuminated; anda circuit for controlling the illumination of each light source suchthat it remains illuminated for a time after its associated sensor hasceased to detect the presence of the object; wherein each of the lightsources is connected with at least one adjacent sensor and isilluminated when the adjacent sensor detects the presence of an objectthereby causing an area of the surface to emit light that corresponds toand is larger than the shape of the object.

The sensors can be proximity sensors, e.g. based on capacitance in thespace above the surface, or contact sensors, e.g. simple switches thatare closed by predetermined pressure applied to the surface. Both typesof sensors are well known and accordingly further description isunnecessary.

The illuminating surface is preferably an array of circuits, eachcircuit comprising at least one sensor and at least one light source.Each circuit preferably includes a single circuit and at least one lightsource. The greater the number of light sources that are controlled byeach sensor, the poorer the definition of the illuminated area will be;on the other hand, the use of two or more light sources for each sensorreduces (as compared to one light source per sensor) the cost and thecomplexity of illuminating the area. In order to simplify the operationof the surface, each circuit has its own power supply and controls itsown light source(s); such an arrangement dispenses with the use of acentral processor to control the illumination of the surface; the use ofsuch a central processor adds greatly to the complexity of theinstallation of an illuminating surface since it requires data lines tobe provided to each light source to control its operation.

As mentioned above, the area of the surface that emits light is largerthan the shape of the object touching or in close proximity to thesurface. This may be achieved by connecting adjacent circuits togetherin such a way that, when the sensor of one circuit (the “detectingcircuit”) detects the presence of the object, the light source of atleast one adjacent circuit is caused to be illuminated. Preferably, thelight source of the adjacent circuit is illuminated after a delayfollowing the illumination of the light source of the detecting surface,thereby giving the effect that the surface that emits light in thepresence of the object is spreading.

When the object is removed from contact or proximity with the surface,the light sources of the relevant circuits cease to be illuminated; itis preferred that the light sources of the adjacent circuits cease to beilluminated prior to the light sources of the detecting circuit, therebygiving the effect that the area of the surface that emits light shrinkswhen the object is no longer touching or adjacent to the surface.

Preferably, each detecting circuit is energisable from a power sourcewhen its sensor detects the presence of an object touching or in closeproximity to the surface, thereby activating the light source of thatcircuit; in a preferred embodiment, current from the detecting circuitcan leak to adjacent circuits, thereby activating the light source ofthe adjacent circuit.

It is preferred that each circuit includes a transistor having a baseterminal, an emitter terminal and a collector terminal, the arrangementbeing such that the light source is illuminated when the transistorbecomes conductive; when the sensor detects the presence of an object,the potential of the base is preferably changed, thereby allowingcurrent to flow through the transistor and so also activating the lightsource to emit light.

Each circuit is preferably connected to the base of the transistor of anadjacent circuit, whereby potential from a detecting circuit can beapplied to the base of the adjacent circuit, thereby rendering thetransistor of the adjacent circuit conductive and hence the light sourceof the adjacent circuit to be activated. Preferably, the connectionbetween each circuit and the base of the transistor of the adjacentcircuit is via a resistor, so that the potential applied to thetransistor base of an adjacent circuit is less than the potentialapplied to the transistor base of the detecting circuit. With such anarrangement, when the potential leaks from the transistor base followingremoval of the object, the light source of the adjacent surface isswitched off prior to the light source of the detecting circuit.

The “object” that will cause the illumination of the surface may notonly be an inanimate object but also a person; when used as a floor, thesurface can be rendered illuminating by walking across it.

The advantage of the present invention is that the area of theilluminating surface that emits light is larger than the area of theobject; since the object will block light from the surface in contactwith the object, such an arrangement increases the level of illuminationprovided by the surface. This is advantageous when the illuminatingsurface is used to light a walker's passage across a room and fordecorative effect.

The light sources will continue to emit light even after the object hasbeen removed; this again increases the level of illumination provided bythe illuminating surface and its decorative effect. In addition, it canbe used for security purposes to show, for example, the passage ofsomeone who has crossed a room.

It is possible to link all or some of the light sources to amicroprocessor so that they can be illuminated prior to a person walkingacross the surface to mark a path across the surface. However, thatrequires conductive paths between the microprocessor and the lightsources that increases the complexity of the system but it is a possibleadditional feature of the present invention if the effect is thoughtworthwhile in view of the additional complexity.

BRIEF DESCRIPTION OF THE DRAWINGS

There will now be described, by way of example only, two embodiments ofan illuminating surface according to the present invention by referenceto the accompanying drawings in which:

FIG. 1 shows an array of circuits forming an illuminating surfaceaccording to the present invention;

FIG. 2 shows the same circuits as FIG. 1 but on an expanded scale;

FIG. 3 is a schematic partial sectional view of a panel having a surfaceaccording to the present invention; and

FIG. 4 shows a further array of circuits forming an illuminating surfaceaccording to the present invention.

DESCRIPTION OF BEST MODE OF OPERATION

Referring initially to FIG. 2, there is shown an array of circuits 10,which are all identical. In view of this, only the components of thecircuit (circuit G) in the top left hand corner of FIG. 2 will be shown.

The circuit comprises a switch 12 connected between a source ofpotential 14 (e.g. about 12 volts so that the floor does not carry highpotential, which could be hazardous) and the base terminal 16 of aDarlington NPN transistor 18. The circuit also includes a light emittingdiode (LED) 20 connected between the transistor 18 and the potentialsource 14; a resistor 22 is included between the potential source 14 andthe light emitting diode 20. A capacitor 24 is connected in parallelwith the switch 12 and a resistor 26 is connected in series between theswitch 12 and the base terminal 16. Lines 28 connect adjacent circuits10 via resistors 30. A connection 32 is introduced between lines 28 ofeach circuit and the resistor 26 so that potential can be applied fromline 28 via resistor 26 to the base terminal 16 of transistor 18.

The emitter terminal of transistor 18 is connected to a negativepotential source or, more generally, to earth.

Transistor 18 is only conductive above a threshold potential applied atbase 16. When the switch 12 is open (as shown) the potential applied tothe base 16 of the transistor 18 is below the threshold and accordinglycurrent cannot flow through the transistor and so LED 20 remainsunilluminated. In this condition, the capacitor 24 will be charged. Whenthe switch 12 is closed, a potential is applied from terminal 14 to thebase 16 via resistor 26 that renders the transistor 18 conductive and socurrent passes through the LED, which emits light. At the same time,capacitor 24 is discharged.

In addition to applying potential to the transistor 18 of its owncircuit, G, the potential from terminal 14 is applied to the fouradjacent circuits C, F, H and K (see FIG. 1) via switch 12 of circuit Gand connections 32, lines 28 and resistors 30 (only circuit K is shownfull in FIG. 2 and for that reason, the following description will makeparticular reference to circuit K but, as is clear from FIG. 1, the samewill also apply to each adjacent circuit). The potential is applied viathe connection 32 and the resistor 26 of each such adjacent circuit tothe base terminal of the transistor 18 of that circuit. The potentialapplied to base 16 is sufficient to cause the transistor 18 to becomeconductive and hence for the LED of adjacent circuit K to emit light.

Because of the presence of resistors 30, the potential applied to base16 of circuit K will be less than that applied to the base 16 of circuitG (assuming the switch 12 of circuit K remains open). In addition, itwill take a greater amount of time for the base terminal 16 of circuit Kto reach the threshold potential due to the need to partially dischargecapacitor 24 of circuit K with the current supply from circuit G. Thus,LED 20 of circuit K starts emitting light slightly after the LED ofcircuit G.

If the switch 12 of circuit K were closed, then the potential at base 16would be the same in circuit K as in circuit G. However, assuming thatthe switch 12 of circuit K is not closed, the lighting up of LED 20 ofcircuit K after LED 20 of circuit G gives the appearance of theilluminated area spreading over time. When the switch 12 of circuit G isopened, the potential applied at bases 16 of circuits G and K fall and,when they reach their threshold values, transistors 18 of the these twocircuits cease to be conductive. Because the potential at base 16 ofcircuit K is lower than that of base G, transistor 18 of circuit Kbecomes non-conductive before that of circuit G (assuming the switch 12of circuit K is never closed). This gives an impression that theilluminated area shrinks and fades from the edge inwards.

The potential at base 16 reduces as a result of the charging of thecapacitor 24 and leakage of potential through other circuits in thenetwork. The duration of the reduction in potential at base 16 to itsthreshold value will depend on the value of resistors 26 and 30 and thecapacitance of the capacitor 24.

Referring now to FIG. 1, if the switch 12 of circuit G were closed, thepotential from source 14 will be applied via a single resistor 30 tocircuits C, F, H and K, thereby causing the LED of those circuits toemit light. The terminal 14 will be connected via two resistors 30 tocircuits B, D, E, J, L and 0. Depending on the value of the resistors 30and 26, that may be sufficient to cause the transistors 18 of thosecircuits to become conductive and so their LED's to emit light.

In a preferred embodiment, the values of the various components are asfollows: resistor 22: 330 ohms resistor 26: 4700 ohms resistor 30: 10 to30 megaohms capacitor 24: 220 nF threshold value of base 16: 1.5 volts

A partial sectional view of a panel having a surface according to thepresent invention is shown schematically in FIG. 3. The panel includes arigid backing sheet 40 supporting the circuits 10 of FIGS. 1 and 2 shownschematically by the reference number 42 in FIG. 3. The switches 12 ofthe circuits of FIGS. 1 and 2 are also shown and they can be closed bythe application of a light pressure to them. The top layer of the panelis formed by a flexible sheet 42 of transparent or translucent plastic44. When a person treads on the panel, the top layer 44 depresses theswitches immediately under the person's foot, thereby closing switches12 and illuminating the LEDs of the associated circuits 10. After aninterval, the area of panel 38 that is illuminated by LEDs spreads toadjacent circuits 10 in the manner described above. When the person'sfoot is lifted, the LED of each circuit will remain illuminated untilthe threshold voltage at the base terminal 16 of that circuit fallsbelow the threshold value. This will happen for circuits 10 whose switch12 are not closed before it occurs in the circuits whose switches 12 areclosed, which will give the effect of the area of the panel illuminatedshrinking over time. The area of the panel 38 that is illuminated byLEDs will correspond generally to the shape of the person's foot (orother object pressing against the sheet 44), although it will of coursebe larger because of the activation of the adjacent circuits, asdescribed above. The resolution of the surface will depend on the numberof LEDs per unit area, which will typically be 1,000 per square metre orabove.

The circuit will generally be provided in the form of panels or tileshaving connectors at their edges to connect to adjacent panels to formthe lines 28 connecting the circuits 10 together across the whole extentof a surface that is larger than each individual panel or tile.

The circuit of FIG. 4 is generally similar to that of FIGS. 1 and 2 andthe same reference numerals will be used in FIG. 4 to refer to the samecomponents that were described in connection with FIGS. 1 and 2 exceptthat in FIG. 4 an apostrophe (′) will be added after the referencenumeral.

The main difference between the circuit of FIG. 4 and that of FIGS. 1and 2 is that the transistor 18′ is a PNP-type transistor instead of theNPN-type transistor 18 used in FIGS. 1 and 2.

The operation of the FIG. 4 circuit is the same as that of FIGS. 1 and 2except as detailed below. Transistor 18′ is only conductive above athreshold potential applied at base 16′. When the switch 12′ is open (asshown) the potential applied to base 16′ of transistor 18′ is below thethreshold and accordingly current cannot flow through the transistor andso LED 20′ remains unilluminated.

When switch 12′ is closed, a potential is applied from terminal 14′ tothe base via resistor 26′ that renders the transistor 18′ conductive andso current passes through the LED, which emits light. At the same time,capacitor 24′ will be charged. As soon as switch 12′ is opened capacitor24′ will slowly discharge, causing LED 20′ to remain illuminated untilcapacitor 24′ is discharged below the threshold potential of transistor18′.

The potential at base 16′ reduces as a result of the discharge of thecapacitor 24′. The duration of the reduction in potential at base 16′ toits threshold value will depend on the value of resistors 26′ and 30′and the capacitance of capacitor 24′.

In the same way as described in connection with FIGS. 1 and 2, when theswitch 12′ of any circuit of FIG. 4 is closed, the neighbouring circuitswill also be illuminated but this will take place after the illuminationin the circuit where the switch is closed. Likewise, when the switch isopened, the illumination of the neighbouring circuits (whose switchesare open all the time) will fade first.

The values of the components of the FIG. 4 circuit are the same as thosegiven for the FIGS. 1 and 2 circuit.

The main advantage of the FIG. 4 circuit over that of FIGS. 1 and 2 liesin the fact that, when first powered up, the LED 20 of circuit of FIGS.1 and 2 is illuminated until the capacitor 24 is charged up. On theother hand, when the circuit of FIG. 4 is first powered up, the LED 20′is not illuminated.

1. An illuminating surface that, when connected to a power source, emitslight in the presence of an object touching or in close proximity to thesurface, which surface comprises: an array of sensors for detecting thepresence of the object; an array of light sources, each sensor beingassociated with at least one light source such that, when one of saidsensors detects the presence of the object, its associated light sourceis illuminated; and a circuit for controlling the illumination of eachlight source such that it remains illuminated for a time after itsassociated sensor has ceased to detect the presence of the object;wherein each of the sensors is connected with at least one adjacentlight source that is illuminated when the sensor detects the presence ofan object, thereby causing an area of the surface to emit light thatcorresponds to and is larger than the shape of the object.
 2. Anilluminating surface as claimed in claim 1, which includes an array ofcircuits, each circuit comprising at least one sensor and at least onelight source.
 3. An illuminating surface as claimed in claim 2, whereineach circuit has its own power supply and is not under the control of acentral processor for the surface.
 4. An illuminating surface as claimedin claim 2 or claim 3, wherein adjacent circuits are connected in such away that, when the sensor of one circuit (the “detecting circuit”)detects the presence of the object touching or adjacent to the surfaceone circuit, at least one adjacent circuit causes its light source to beilluminated.
 5. An illuminating surface as claimed in claim 4, whereinthe light source of the said at least one adjacent circuit isilluminated after a delay following the illumination of the light sourceof the said detecting circuit, thereby giving the effect that the areaof the surface that emits light in the presence of the object spreads.6. An illuminating surface as claimed in claim 4 or 5, wherein the lightsource of the said at least one adjacent circuit ceases to beilluminated prior to the light source of the said detecting circuit,thereby giving the effect that the area of the surface that emits lightshrinks when the object is no longer touching or adjacent to thesurface.
 7. An illuminating surface as claimed in any one of claims 4 to6, wherein each detecting circuit is energisable from a power sourcewhen its sensor detects the presence of an object touching or in closeproximity to the surface, thereby illuminating the light source of thatcircuit.
 8. An illuminating surface as claimed in claim 7, whereincurrent from the said detecting circuit leaks to at least one adjacentcircuit, thereby energising the light source of the adjacent circuit. 9.An illuminating surface as claimed in any one of claims 4 to 8, whereineach circuit comprises a transistor having a base terminal, thearrangement is such that the light source is illuminated when thetransistor is conductive and wherein, when the sensor detects theobject, the potential at the base terminal is changed, thereby causingthe transistor to become conductive.
 10. An illuminating surface asclaimed in claim 9, wherein each circuit is connected to the base of thetransistor of the at least one adjacent circuit, whereby potential froma detecting circuit is applied to the transistor base terminal of theadjacent circuit, thereby changing the potential of the adjacent circuittransistor base terminal, allowing current to flow through thetransistor of the adjacent circuit and causing the light source of theadjacent circuit to be illuminated.
 11. An illuminating surface asclaimed in claim 10, wherein the detecting circuit is connected to thebase of the transistor of the at least one adjacent circuit via aresistor such that the potential applied to the base of the transistorof the at least one adjacent circuit is less than the potential appliedto the base of the transistor of the detecting circuit.
 12. Anilluminating surface as claimed in any one of claims 1 to 11, whereinthe sensors are switches that are closed by the object touching thesurface.
 13. An illuminating surface as claimed in any one of claims 1to 12 in the form of a floor or wall tile.
 14. An illuminating surfaceas claimed in any one of claims 1 to 13 connected to a power source.